BACKGROUND: Syrian refugees resettled in Turkey show a high prevalence of symptoms of mental disorders. Problem Management Plus (PM+) is an effective psychological intervention delivered by non-specialist health care providers which has shown to decrease psychological distress among people exposed to adversity. In this single-blind pilot randomised controlled trial, we examined the methodological trial procedures of Group PM+ (gPM+) among Syrian refugees with psychological distress in Istanbul, Turkey, and assessed feasibility, acceptability, perceived impact and the potential cost-effectiveness of the intervention. METHODS: Refugees with psychological distress (Kessler Psychological Distress Scale, K10 > 15) and impaired psychosocial functioning (World Health Organization Disability Assessment Schedule, WHODAS 2.0 > 16) were recruited from the community and randomised to either gPM+ and enhanced care as usual (E-CAU) (n = 24) or E-CAU only (n = 22). gPM+ comprised of five weekly group sessions with eight to ten participants per group. Acceptability and feasibility of the intervention were assessed through semi-structured interviews. The primary outcome at 3-month follow-up was symptoms of depression and anxiety (Hopkins Symptoms Checklist-25). Psychosocial functioning (WHODAS 2.0), symptoms of posttraumatic stress disorder and self-identified problems (Psychological Outcomes Profiles, PSYCHLOPS) were included as secondary outcomes. A modified version of the Client Service Receipt Inventory was used to document changes in the costs of health service utilisation as well as productivity losses. RESULTS: There were no barriers experienced in recruiting study participants and in randomising them into the respective study arms. Retention in gPM+ was high (75%). Qualitative analyses of the interviews with the participants showed that Syrian refugees had a positive view on the content, implementation and format of gPM+. No adverse events were reported during the implementation. The study was not powered to detect an effect. No significant difference between gPM+ and E-CAU group on primary and secondary outcome measures, or in economic impacts were found. CONCLUSIONS: gPM+ delivered by non-specialist peer providers seemed to be an acceptable, feasible and safe intervention for Syrian refugees in Turkey with elevated levels of psychological distress. This pilot RCT sets the stage for a fully powered RCT. TRIAL REGISTRATION: ClinicalTrials.gov Identifier NCT03567083 ; date: 25/06/2018.